This invention relates to a method and apparatus of monitoring the soot level in a diesel particulate filter.
Diesel engines employed in commercial vehicles typically have filters arranged in the exhaust system to filter particulate matter from the exhaust to comply with emissions standards. The filter may be used numerous times after it has become saturated before a new filter must be installed. There is a need to measure the level of soot loading in diesel particulate filters (DPF) for determining when it is time to perform a filter regeneration cycle in which soot is removed from the filter when it has become too clogged. There is also a need to determine if the filter is incapable of performing adequately such that regeneration may not be successfully performed due to a failure (breakdown, burn-through, etc.) of the substrate.
Present methodology for determining a filter's state is to measure the pressure drop across the filter. The pressure drop across a filter increases as the filter load increases. At some pre-determined pressure drop, the filter is run through a regeneration cycle. This methodology has drawbacks. The rate of filter loading influences the pressure drop behavior such that the filter may appear to be in need of regeneration later or sooner than necessary. Also, a breakdown or burn-through of the substrate leads to a low pressure drop “bypass” mode, which may be interpreted as a clean filter and would result in a significant blow-by and loss of filtering capability. Therefore, a more reliable method and apparatus are needed to determine the state of the DPF.